Method for the production of assemblies comprising titanium



United 3 074 858 METHOD FOR THE PR ODiJCTION F ASSEMBLIES COMPRISINGTITANIUM Frank Riding, Widnes, England, assignor to Imperial atent3,074,858 Patented Jan. 22, 1963 ice Chemical Industries Limited,London, England, a cor- 5 an electrodeposit, of platinum or rhodium.poration of Great Britain According to the present invention the methodfor the N0 Drawillg- Filed 1969, 18,397 production of an assembly inwhich there is electrical Claims P y, pp f great Britain P 15, 1959contact between titanium and graphite comprises pro- 6 Claimsviding thesurface of the titanium to face the graphite The present inventionrelates to improvements in or 10 t deposited f i g Of a platinum metalprior to relating to a method for the production of assemblies hnhglhgthe tltehlum and graphite Into 531d eleetrleal comprising titanium andparticularly to a method for eohtaetthe production of assembliesinvolving contact between PYeteTah1Y S a1d Surface of t tltanlhm isetched P titanium and graphite as for instance in an interference to thedepoeltloh Q the Platlhhm metal- Furthermore: fit preferably theplatinum metal is electrodeposited on an Experiments using a laboratorycell producing chlorine etched Surface of tttflhhlmby electrolysis ofbrine have shown that it would be pos- Y the term f P Platlhhm metal 18meant sible for example to design a titanium rod screw-fitting Plahhum,rhodtum, lndlum an alloy of two into a graphite anode or a graphite rodcontacting a more of these Pe I titanium anode which would besatisfactory with regard 20 T tenth htahluhn {hchldes a tltahlum alloyto the voltage loss at the metal to graphite contact. Proslstmgessehhally of tltahlhmlonged electrolysis at a high anodic currentdensity has By Way of exemple the method of the If lhveh' shownfurthermore no apparent change in the smooth be applied to a lhercurycell having an anode bright Surface of atitanium rod or anode 1 7.7mches long of platinum coated expanded sheet Measurements of theelectrical contact resistance up f clalmed Inter aha eopehdihg PP tovery high contact pressures (3600 lb./in. have non Senal 3 filed ruary17, 1959, and shown however that at a contact pressure of even 3600graphlte current lead'm rods; These rode can he 9 lb./in. thetitanium-graphite contact resistance is about nficted to anode ofhlatfmsed expanded sheet 2.5 times the graphite-graphite resistance at25 lb./in. F by Welding to t tltamum F of h anode four Nevertheless in,for instance, the field of chlorine promanmm.cups of for Instance L240mte.ma1 diamduction by electrolysis of brine it would be desirable, foreter whlch, accommodate the griphlte lead'm rods. by example, to be ableto utilise titanium as a substitute for a I Interference and Whlch haveh prqvlded the graphite at present used as current IeaMn rods on thenlnner surfaces w1th an electredeposit of platmum. cause in titaniumthere is absence of porosity, it has By measiunng Potential drops ivenous cutl'ehts the greater mechanical strength and electricalconductivity, contact resistance has been determined for both machinedit has high resistance to corrosion by chlorinated brine cuPS ahdstamped P havlhg Parental and Shghtty and Wet chlorine gas and becauseit has an ability to verging sides respectlvely when the inner surfaceof these act as an insulator to an electrolyte whilst, at the same cupshave and have an electfodeposlt of platthum' time, it is able to passcurrent to an electronic conductor. T F rechrded the tenowlhg table eexpressed The object of the present invention is to provide a 40 inmlllivolts per ka./m. anodic current density. method of loweringelectrical contact resistance between titanium and graphite inassemblies of titanium and Cup Without With hit platinum platinumExperiments have therefore been carried out to measure the titanium tographite electrical contact resistance g gg gg eg 2 at various contactpressures for titanium etched with anap lytical reagent qualityconcentrated hydrochloric acid for 4 days, similarly etched followed byrhodium electrm These values show the marked superiority of theelecdeposition, similarly etched followed by platinum electrodeposltedPlatinum coated titanium t0 graphite C011 trodeposition, similarlyetched followed by five coats of tact as against a titanium t0 graphiteContact and 3150 a paint applied platinum-bearing preparation with the wthat the Stamped P, Where the interference is fi i f each applied coatat 500 C and nometched maintained throughout insertion of the graphitelead-in treated with 20 coats of the same platinum-bearing preprod, 15the better designti ith th fi i f h coat li d at 500 C, Similar resultsare obtained on passing the current in In the following table there isrecorded the results obthe pp direction titanium t0 graphite) inditainedfor variations of titanium to graphite contact eating the absence of yrectifying P p resistance in ohms-cm. with contact pressure at room WhatI claim is; temperature. 1. A method for the production of an assemblyin Paint Paint Electro- Electro- Etched applied applied depositeddeposited Contact pressure Graphite Titanium titanium platinum platinumrhodium platinum -I1 t0 '0 to on etched on nonon etched on etchedgraphite graphite graphite titanium etched titanium titanium to titaniumto to graphite to graphite graphite graphite -coated titanium andgraphite into said electrical contact.

2. A method as claimed in claim 1 wherein said surface of the titaniumis etched prior to the deposition of the coating of a platinum metal.

3. A method as claimed in claim 2 wherein the coat- "ing of platinummetal on the etched surface of titanium is elfected byelectrodeposition.

4. An assembly for the passage of electrical current therethrough, saidassembly comprising a body of titanium, a surface of which has aplatinum metal coating deposited thereon, a graphite body and means formaintaining said graphite body and said titanium body in 'electricalcontact under pressure directly through said coating whereby theelectrical contact resistance between 'said graphite body and titaniumbody is decreased.

5. The assembly of claim 4 wherein said titanium member'is a cup, theinner surface of which is provided with said coating and said graphitemember is a rod fitted into said cup for electrical contact.

'6. In a mercury cell, an anode assembly comprising a body of titanium,a surface of which has a platinum metal coating deposited thereon, agraphite body and means for maintaining said graphite body and saidtitanium body in electrical contact under pressure directly through saidcoating whereby the electrical contact resistance between said graphitebody and titanium body is decreased.

References Cited in the file of this patent UNITED STATES PATENTS2,624,772 Phillips Jan. 6, 1953 2,631,115 Fox Mar. 10,1953 2,636,856Suggs et al Apr. 28, 1953 2,829,091 Missel Apr. 1, 1958 2,873,233Schnable Feb. 10, 1959 OTHER REFERENCES Chemical Age, Jan. 3, 1959, page9.

1. A METHOD FOR THE PRODUCTION OF AN ASSEMBLY IN WHICH THERE ISELECTRICAL CONTACT BETWEEN TITANIUM AND GRAPHITE WHICH COMPRISESPROVIDING THE SURFACE OF THE TITANIUM TO FACE GRAPHITE WITH A DEPOSITEDCOATING OF A PLATINUM METAL AND THEREAFTER BRINGING THE PLATINUMCOATEDTITANIUM AND GRAPHITE INTO SAID ELECTRICAL CONTACT.